code: def ensure_dataframe(X):
      assert X is not None
      if isinstance(X, list):
          return pd.DataFrame(X)
      elif isinstance(X, np.ndarray):
          return pd.DataFrame(X)
      elif isinstance(X, pd.Series):
          return pd.DataFrame(X)
      elif isinstance(X, pd.DataFrame):
          return X
      raise ValueError("Failed to convert to Series")
  
file_path: fairlearn/test/unit/input_convertors.py
imports: import numpy
  import pandas
  from fairlearn.utils._input_validation import _merge_columns
label_desc: Use image node_id 6 for calling a global function with example usage: ensure_dataframe(X) and returns: pd, pd, pd, X